1. Field of the Invention
The present invention relates to a Liquid-Crystal Display (LCD) device. More particularly, the invention relates to a LCD device having a color filter in which a color layer, a light-shielding layer, and a protection or overcoat layer are formed, or a LCD device having a monochrome filter in which a light-shielding layer and a protection (or overcoat) layer are formed.
2. Description of the Related Art
A prior-art color filter having a color layer, a light-shielding layer, and a protection layer for protecting the light-shielding layer is disclosed in the Japanese Non-Examined Patent Publication No. 11-305216 published in Nov. 5, 1999. This filter comprises a transparent plate, a patterned light-shielding layer, a patterned color filter layer (which may be termed a “color layer”), a protrusion layer, and an overcoat layer.
The light-shielding layer, which is matrix-shaped, is formed on a surface of the plate. The color filter layer (color layer), which is patterned to form pixels, is formed on the exposed areas of the surface of the plate from the light-shielding layer. The protrusion layer is formed by dot-shaped protrusions arranged on the matrix-shaped light-shielding layer. The protrusions serve as spacers arranged between the pair of transparent plates of the LCD device. The overcoat layer is formed over the whole surface of the plate to cover the light-shielding layer, the color filter layer, and the protrusion layer. The overcoat layer serves as a protection layer.
The above-described prior-art color filter is preferably used for IPS (In-Plane Switching) mode LCD devices. The overcoat layer in this color filter prevents some substances in the light-shielding layer, the color filter layer, and/or the protrusion layer from eluting. When this color filter is incorporated into an IPS-mode LCD device, the overcoat layer will prevents a trace of alkali metal ions and/or other unwanted substances from eluting into the liquid crystal. Thus, malfunction of the liquid crystal due to the alkali metal ions and/or other unwanted substances is avoided.